1. Field of the Invention
The invention provides an apparatus for determining blood loss in a patient, particularly a patient undergoing an operation, such that the need for and amount of a blood transfusion can be determined. The blood loss monitor is envisioned primarily for use with human patients, but also may be utilized for other animals, particularly in research. In accordance with the present invention, the amount of blood lost during a surgical procedure can be substantially continuously monitored as the operation or procedure progresses.
2. Discussion of the Background
During a surgical operation or procedure, it is extremely important to determine the amount of blood lost by the patient. In particular, it is important to avoid the use of a blood transfusion when unnecessary, to conserve blood supplies and also to avoid potential risks to the patient associated with exposure to blood which may contain contaminants or undetected viruses. However, where the blood loss is significant, a transfusion must be utilized to ensure the patient's well-being.
Often it is difficult to determine the precise amount of blood loss during an operation. For example, where the surgeon or anesthesiologist are tending to other matters, it is difficult to concentrate on the amount of blood lost, particularly during operations which involve large blood losses. In addition, mere visual observation is typically inaccurate. Nevertheless, transfusion practices often vary, and frequently are based upon a subjective assessment by the physician. In the past, physicians have often utilized a liberal approach to transfusions, with the philosophy that it is better to "stay ahead" than lag behind with regard to the patient's blood level. However, this can be wasteful to the overall blood supply, and perhaps more importantly, might unnecessarily expose the patient to infectious diseases. Moreover, an unnecessary transfusion could also result in less than optimal conditions for the patient, which can be particularly important during surgery. Thus, an apparatus for determining the amount of blood loss during a surgical operation or procedure is needed.
U.S. Pat. No. 4,773,423 to Hakky describes an arrangement for determining blood loss in which blood is collected by a vacuum tube, and is urged or squeezed from collected swabs or other material, and thereafter, the amount of blood loss is determined by the hemoglobin content. However, this arrangement has two significant problems. First, it is difficult to gather all of the blood lost by the patient by direct vacuum or by squeezing the blood from swabs or sponges utilized during surgery. Thus, in the Hakky arrangement, the amount of blood gathered does not reasonably approximate the entire amount of blood lost. In addition, the Hakky arrangement relies upon a direct color measurement of the reagent solution, and such a direct measurement can be quite inaccurate. For example, hemoglobin is generally a mixture of varying forms, each having different absorption spectrums. In addition, any fluid obtained from the patient will also include a variety of dissolved and solid impurities, and the turbidity of the sample can complicate direct colorimetric measurement. Thus, a direct color measurement of a solution will not provide a reliable indication of the amount of blood loss during surgery.
Accordingly, an apparatus which can accurately and rapidly provide a reliable indication of the amount of blood lost during a surgical operation or procedure is needed. Such an arrangement should be relatively easy to operate, and should provide a fairly immediate approximation of the amount of blood loss to inform the physician, and allow him or her to determine whether a blood transfusion is necessary.